FOXSports Sabermetrics Glossary

There are many advanced baseball statistics that can help you forecast player performance; below are a dozen that will help you start down the road to fantasy glory. We could probably write entire articles on each of them, but consider this an introduction. And remember: No number represents an absolute guarantee of anything.

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BABIP (Batting Average on Balls in Play)

For hitters: An at bat can result in a home run, a strikeout, or a ball “in play.” In 2013, the average BABIP for hitters was .297, and it’s usually somewhere around .300. Why do we care? Because extreme BABIPs – like .250 or .350 – are usually indicators of bad luck and good luck, respectively. Over a short period, or even a season, a very strong BABIP suggests that a batter is experiencing some good fortune in “hitting ‘em where they ain’t,” and a weak BABIP the opposite. This luck factor will mainly affect batting average, but runs scored, RBI and stolen bases are impacted as well.

Let’s take Mets 1B Ike Davis. His BABIP in 2012 was .246, which was the second-worst mark in the majors, and a big factor in his .227 batting average. If Davis had a track record of bad BABIPs, we could attribute it to something like an inability to make good contact. However, Davis’ BABIPs with the Mets in 2010 and 2011 were .321 and .344, and he posted BABIPs of .318, .348 and .381 at extended stops in the minors. While there are no guarantees that Davis’ 2012 BABIP will improve, it probably will. Keep this in mind when your competitors are spooked on draft day by his bad batting average.

Can other factors affect a hitter’s BABIP? Sure. A ballpark with a large outfield – Coors Field, for example – will see more hits drop in. Fast runners that get many infield hits (like Brett Gardner) and batters with high line-drive rates (like Joey Votto) tend to have above-average BABIPs, and the converse is true for slow guys who hit the ball in the air a lot. But for most players, we should assume a BABIP close to .300.

For pitchers: BABIP is even more important here, because the pitcher has less control over what will happen when the ball is hit. That’s why high-strikeout pitchers are more reliable – a strikeout isn’t subject to a weak fly ball falling in front of an outfielder, or getting past a slow shortstop.

You might be thinking, “This is stupid, because great pitchers induce weak contact.” This may be true … to a point. Some aces (like Clayton Kershaw and Matt Cain) have consistently low BABIPs. However, the MLB average for pitcher BABIP in 2012 was .293, and Stephen Strasburg’s was .311. Sometimes, you just have bad luck.

Again, while we can’t predict BABIP, we can assume that most guys will have a number that settles near the league average, and/or near their career averages (which should also be looked at). Good or bad defense can have an effect, as can letting batters rip line drives everywhere (like Ricky Nolasco). Otherwise, we can look at a guy like Adam Wainwright – who had a .315 BABIP in 2012 (fifth-worst in MLB) but carries a .293 career mark – and reasonably figure that his 3.94 ERA will drop by a lot.

For both: For a number of reasons, there are hitters and pitchers with BABIPs that consistently defy the league averages. Your focus should be on the outliers – BABIPs that stick out like a sore thumb in someone’s stat line. Torii Hunter’s career BABIP is a pretty normal .307, so why was it .389 last season? Luck, most likely.

LOB% (Percentage of Runners Left on Base)

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For pitchers: This is the percentage of runners a pitcher strands on base over the course of a season. LOB averages are usually 70-72 percent, and last year’s MLB average was 72.5%. While your ace-level, high-strikeout guys will tend to have higher-than-average LOB rates – because they retire more batters whether or not runners are on base – most pitchers will regress toward league average.

Example: Tampa Bay’s Jeremy Hellickson led MLB with an 82.7 LOB% in 2012, and was second (82%) in 2011. Is it possible that Hellickson has an innate ability – better than anyone else’s over the last 40-some years – to pitch amazingly well with runners on base? Sure, but it’s not likely. Hellickson’s BABIPs have been historically low, and maybe he’ll be an exception to these rules. However, his luck is probably about to turn to some extent. The LOB% can’t stay this good.

GB% (Percentage of Ground Balls to Balls in Play)

For pitchers: The average MLB ground-ball rate in 2012 was 45.1 percent. Even though ground-ballers can be punished by bad fielders, generally a strikeout/ground-ball combo is good, because it keeps balls from going over fences. Even a ball in play is better than a home run from a pitcher’s perspective, right?

The top five ground ballers in 2012 were Trevor Cahill (61.2 GB%, 3.78 ERA), Jake Westbrook (58.1, 3.97), Lucas Harrell (57.2, 3.76), Henderson Alvarez (57, 4.85) and A.J. Burnett (56.9, 3.51), and their ERAs were all over the board. However, Burnett is a good example of how posting above average numbers in both K% and GB% can lead to success. David Price and James Shields are better starters who were very good in both categories. Ground balls by themselves are not a good indicator of performance, but by inherently allowing fewer homers, pitchers who keep the ball on the ground have a head start over their fly-balling counterparts.

HR/FB% (Fly Ball to Home Run Ratio)

For pitchers: This is the numbers of home runs given up per every fly ball allowed. Pitchers with home games in small ballparks will tend to have higher HR/FB ratios, with the opposite in larger parks, but generally the average is close to 10 percent (last year’s was 11.3). If you see an extreme HR/FB rate – like Gio Gonzalez’s 5.8 from last season – you should remember that it’s more likely to regress toward the league average than to stay where it is.

For hitters: Batters have more control over HR/FB ratios, because some guys just hit the ball farther than others – like Adam Dunn, who has a career HR/FB rate of 22 percent. Also, slappy guys who hit singles all the time will tend to have lower HR/FB rates. This is a better stat for judging pitchers than hitters.

However, outliers still exist here. Hey, Chase Headley – why did you post a 21.4 HR/FB rate in 2012 (10th-best in MLB) after maxing out at 10.7 percent in your four previous seasons? Maybe you got stronger, but maybe you got a little lucky. We’re not expecting 30-plus homers again, big guy.

K/BB (Strikeout to Walk Ratio)

For pitchers: Unless you want to trust a more encompassing stat like FIP or xFIP (which we encourage), K/BB is a nice, easy rule of thumb you can use to predict a pitcher’s effectiveness. Thanks to our strikeout-happy era, last year’s ratio of 2.5 strikeouts to every walk was the highest of all time.

While K/BB is helpful, if the strikeout rate isn’t high enough – maybe 7.5 whiffs per nine innings or better – a pitcher will be subject to the previously mentioned luck factors. Still, only two of 2012’s top 20 K/BB pitchers – Joe Blanton (4.88 K/BB, 4.71 ERA) and Dan Haren (3.74 K/BB, 4.33 ERA) had ERAs above 3.74. That’s pretty good, and speaks to the general effectiveness of a pitcher who strikes people out and limits free passes. Some people think K/BB should be tweaked a little, but as is, it helps.

Strikeout per nine innings (K/9) and Strikeout Rate (K%)

Though used for both pitchers and batters, this stat is more indicative of a pitchers’ performance, measuring how many strikeouts are averaged over nine innings. As a punch-out is one of the few outcomes pitchers can control, the higher the rate, the better, and improvement in this category likely correlates to an enhanced ERA and WHIP. (For example, part of R.A. Dickey’s 2012 success can be attributed to his jump from a 5.78 K/9 in 2011 to an 8.86 mark last season.)

The league mean is around seven strikeouts per nine innings, with an average above eight considered solid and below six deemed poor. Max Scherzer led all starters last season with an 11.08 K/9 rate.

In reference to batters, a strikeout rate is the more envied approach, as it accounts for plate appearances. A high strikeout rate is not always a red flag, as power hitters tend to have inflated figures, yet an enlarged strikeout percentage versus past production is a signal of hitter regression. The league average is around 19 percent, with a number under 13 percent considered good and over 21 percent deemed bad. Adam Dunn led the majors with a 34.2 strikeout percentage last season, while Marco Scutaro had a league-low 7.2 percentage.

Isolated power (ISO)

To obtain isolated power, subtract a player’s batting average from slugging percentage. This number illustrates a player’s extra-base hits and offers a window into a player’s strength and power.

ISO is better used as a forecast tool, in the sense of what to expect from extra-base production. Though it can be utilized to show what a rising star is capable of, it’s better application is to denote when a slugger is heading for regression. For example, though he’s battled injuries and other off-the-field inquiries, Alex Rodriguez’s ISO has dropped the last five seasons, which is expected of someone his age.

League average hovers around .148, with a mark above .200 deemed solid and below .110 substandard. Josh Hamilton led the majors in 2012 with a .292 ISO.

Line Drive percentage (LD%)

Simply, how many batted balls are deemed line drives? According to Fangraphs.com, a line drive produces 1.26 runs per out, compared to 0.13 runs from fly balls and 0.05 runs for grounders. Basically, hitters are striving for liners while pitchers try to avoid them.

The league mean for line-drive percentage is around .20, meaning pitchers that are under this figure are usually successful, whereas a higher concession of liners translates to failure. (For hitters, the opposite is true.)

If a pitcher unexpectedly struggles, a look at his line-drive percentage can give a sense of the issues. For batters, a high line-drive percentage should signal a robust batting average, as the trajectory of these shots, compared to grounders and fly balls, are the most likely to be hits.

Fielding Independent Pitching (FIP)

Measures three outcomes that pitchers are responsible for – walks, home runs and strikeouts as, to some degree, every other result is a product of chance. A homer does the most damage, while a walk has more impact than a strikeout. FIP highlights a pitcher’s performance apart from his team’s defense and computes to a number similarly digested as ERA. This number illustrates how well a pitcher should have performed over a given period of time.

Major discrepancy between a pitcher’s FIP and ERA can assist as an indicator for future progression or regression, as a FIP higher than ERA signals luck was involved, whereas a lower FIP screams misfortune. (Note: this is not always the case, as Johnny Cueto and Jeremy Hellickson have posted consecutive years of significantly lower ERAs than their FIP marks dictated.)

On the FIP scale, a 4.00 is considered the mean, with a 3.30 or lower considered good and anything above 4.30 as deficient. Gio Gonzalez led baseball with a 2.82 FIP last season, which hovered around his 2.89 ERA. However, David Price’s 3.05 FIP, which was third-best in the American League, was significantly higher than his 2.56 ERA, meaning Price wasn’t as strong as believed last season.

On-base plus slugging (OPS)

The equation is in the namesake, as a player’s on-base percentage is added to his slugging percentage to get this metric. Important figure as it accounts for plate discipline, contact ability, and power. In 2012, major-league average for OPS hovered around .725, with .850 and above considered commendable and anything below .680 to be poor. Miguel Cabrera led the league with a .999 figure, though Joey Votto posted a 1.041 mark (failed to hit the minimum-appearance threshold).

Unfortunately, this stat is not considered the best of barometers, as it’s been determined that OBP is nearly twice as important in association to run production as SLG; alas, this equation treats both factors as equals. Because of this, a metric called adjusted on-base plus slugging (OPS+) is considered a better gauge of a player’s value, as it also takes park factors into consideration.

Nevertheless, because of its simplicity, OPS is the wider known and more commonly used statistic.